It is known to use the material bed roll mill with single or multiple circulation for grinding iron ore or iron ore concentrate to of pelletizing fineness. However, a pelletizable product can only be produced on the material bed roll mill in this way with appropriate pre-treatment of the feed material. In this case, it is necessary in particular to eliminate the oversize material with a particle size greater than 100 μm. Grinding of concentrate with a particle size of more than approximately 200 μm to pelletizing fineness is not possible with this method.
Material bed roll mills are not currently used in closed circuit with classifying assemblies for grinding iron ore or iron ore concentrate, since this is not currently considered to be feasible or economical.
In wet classification, the entire liquid cyclone underflow must be returned to the material bed roll mill. As a result, moisture contents of the feed would be produced in the material bed roll mill at which the material would no longer be drawn in. However, filtration of the entire cyclone underflow in order to reduce the moisture content would be uneconomical.